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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <!--ES5语法-->
    <script type="text/javascript">
        var a = "abcde";
        var b = "千古壹号";
        var c = "123123";
        var d = '哈哈哈哈哈';
        var e = ""; //空字符串

        //var f = haha; // 没使用引号，到这里会直接报错。因为会被认为是js代码，但是之前并没有定义 haha。

        console.log(typeof a);
        console.log(typeof b);
        console.log(typeof c);
        console.log(typeof d);
        console.log(typeof e);
    </script>
</body>

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